The present invention generally relates to manufacturing tools and procedures. More specifically, the present invention relates to a precision cleaning apparatus and process that can be integrated directly into various manufacturing tools and processes. Manufacturing tools and processes requiring precision cleaning include, among others, die attachment, machining, board cutting, wafer singulation, assembly, rework, inspection, wire bonding, adhesive bonding, soldering, underfilling, dispensing, sealing, dicing, coating and trimming tools. These tools may be designed and developed as stand-alone tools, located on automation lines or integrated into existing Original Equipment of Manufacturers (OEM) tools.
In-situ cleaning processes practiced in the prior art involve a variety of cleaning methods including solvent bathes, aqueous cleaning, ultrasonic cleaning, and liquid spraying. Due to there inherent incompatibilities with process tools, the aforementioned methods are typically performed as a step before or after a manufacturing tool or process. For example, U.S. Pat. No. 4,832,753 issued to Cherry et al., suggests a fully enclosed environmental chamber containing a Freon® 113 solvent sprayer with a high-efficiency particulate air (HEPA) filter and dry air re-circulated within a closed chamber. The apparatus is typical of what would be commonly used as a stand-alone cleaning tool within a manufacturing operation.
There are several examples of the prior art suggesting techniques to integrate carbon dioxide snow into substantially stand-alone cleaning systems to control thermal and electrostatic effects during the use of cryogenic impingement sprays. These techniques include using secondary heated or ionized jets or sprays directed at the substrate surface and delivered either independently or as a component of the cryogenic spray. For example, U.S. Pat. No. 5,354,384 issued to Sneed et al. suggests the use of a heated gas, such as filtered nitrogen, to provide both a pre-heat cycle and a post-heat cycle to a portion of a substrate in a snow spray cleaning process. This approach relies on “banking heat” into the substrate portion prior to the cryogenic spray cleaning by delivering a heated gas stream to a portion of the substrate to prevent moisture deposition and adding heat from a heated gas following cryogenic spray treatment. Another example includes U.S. Pat. No. 5,409,418 issued to Krone-Schmidt et al., which suggests an apparatus for surrounding an impinging cryogenic spray stream with an ionized inert gas. It is proposed by surrounding a stream of solid-gas carbon dioxide with a circular stream of ionized gas and applying the two components to the substrate simultaneously, resulting in controlling or eliminating the electrostatic discharge at the surface during impingement. However, in practice, entrainment and deposition of atmospheric contaminants onto substrate surfaces being treated with the cryogenic spray is resulted. As such, cryogenic spray cleaning applications of the prior art necessitate that the housing of the cryogenic spray applicator, the substrate and the secondary gas jets be enclosed in large, bulky and complex environmental enclosures employing HEPA filtration and dry inert atmospheres.
Another approach is to integrate the cryogenic spray cleaning process into a production tool. For example U.S. Pat. No. 5,001,873 teaches a method for cleaning small Excimer LASER optics in-situ within the sealed chamber comprising the LASER cavity itself Using this invention, each optical surface is provided an individual carbon dioxide spray nozzle, as well as purge gas nozzles, as a means for cleaning particle debris from the optical surfaces between LASER operations. Such an invention provides in-situ cleaning of the production tool components, in this case the LASER optical surfaces. However, the '873 invention does not teach an apparatus for generating and controlled such a cleaning spray. More importantly, '873 does not teach providing in-situ spray cleaning of Excimer LASER processed substrates and does not provide a means for integrating cryogenic spray cleaning into the LASER production process.
The failure in the prior art to effectively provide a technology capable of operating within the production process, the same workcell or process tool to provide clean-in-place capability results in a number of disadvantages and limitations in manufacturing operations. As discussed herein, overall productivity is limited by many factors including environmental control challenges for cryogenic spray cleaning, carbon dioxide cleaning machine's ability to operated autonomously, adaptability to different manufacturing processes and tools, cleaning complex surfaces, and cleaning multiple surfaces at one time.
This is particularly disadvantageous in flexible manufacturing systems in which the entire machining operation is intended to be completely automated. Flexible manufacturing systems are designed to operate without human assistance, or greatly reduced human assistance, and it substantially limits their efficiency if a worker must regularly remove substrates, clean them and return them to the manufacturing tool or line.
In another invention by the present inventor, U.S. Pat. No. 5,725,154, the use of a coaxial solid spray generator to spray clean critical surfaces is taught. The '154 invention suffers from the same limitations of other prior art discussed herein including the need for environmental control as well as the need for utilitarian improvements necessary for integration into and control by a production tool. For example, significant improvements in the present invention over '154 include a gas-to-liquid phase condenser and purification system which allows the present invention to be used anywhere in the manufacturing environment with just a single source supply of carbon dioxide gas. This is a particular advantage in manufacturing environments where the transport or storage of high pressure liquid carbon dioxide supply tanks would be cumbersome or pose a risk to workers. Moreover, gas supply lines may be brought from a single supply tank to multiple production tools incorporating the present invention.
Moreover, a new type of capillary condenser technology is taught herein called a “stepped capillary condenser”, which achieves solid carbon dioxide particle types (i.e., particle size and coarseness) heretofore not possible using '154. Conventional snow cleaning devices produce fine gas-filled solid particles, of which a significant quantity of particles are needed to efficiently clean a surface. Moreover, fine particles require extremely high velocities to dislodge tenacious surface contaminants. By contrast, the more coarse particles generated by the stepped capillary condenser embodiment of present invention provide increased physicochemical cleaning action and fewer of these types of particles required to remove very tenacious surface residues.
Still moreover, further research by the present inventor has shown that oscillating the snow particle stream at greater than 1 Hertz significantly improves surface cleaning action (i.e., scouring) with the added benefit of not interrupting the generation and flow of solid carbon dioxide particles. Finally, a means for multiplexing coaxial spray applicators is taught, which provides a method for cleaning multiple sides of a complex article.
Unlike the prior art, the present invention provides the ability to seamlessly integrate cryogenic spray cleaning into a production process. There are many manufacturing applications where such a capability as in the present invention would improve quality and performance, provide a lower cost of ownership and longer tool life (i.e., cutting and dicing blades), smaller footprint, less cleanroom floor space, and provide an increase in process efficiency. One such example is described as follows.
The growing variety and complexity of matrix array packages present a true challenge to many back end processes. The singulation (i.e., dicing a wafer into discrete dies) of these arrays into individual packages is an important step in the manufacturing process, and as in many cases, needs to be optimized to minimize the overall cost of package. The continuous reduction in package size, along with the demand for increased throughput has resulted in a shift to advanced dicing processes for many matrix array packages, for example copper-ceramic and copper-plastic packages. Quality issues associated with conventional dicing of such devices using water-based coolant include chipping along the edges of the diced kerf, smearing of the ductile copper, and the formation of burrs. Using the selective impingement cleaning apparatus of the present invention, a dicing-cleaning hybrid system improves cutting quality, reduces chipping, reduces smearing and burr formation. Another advantage is increased tool life as well since the tool itself is continuously cleaned during the process.
Today's production environment demands fairly autonomous operation and standard control and communication between production controls and equipment to improve efficiency, increase quality and reduce manufacturing costs. These so-called plug and play manufacturing tools utilize standards such as the Generic Model for Communications and Control of Semi Equipment, the Semiconductor GEM standard. No prior art teaches a module which combines all the necessary elements for efficient use of solid phase carbon dioxide spray cleaning in production tools and on the manufacturing line.
As such there is a present need for a plug and play process, apparatus and chemistry that reduces air pollution, eliminates worker exposure hazards, eliminates liquid hazardous waste production, and enables the widespread implementation of in-situ precision cleaning or more specifically clean-during-processing capability.
In many manufacturing operations a product is cleaned prior to or following a particular assembly process, sometimes many times through the production cycle. Conventional parts cleaning operations are performed as an independent operation prior to or following a manufacturing process using, for example, a spray cleaner, vapor degreaser or ultrasonic cleaning system. Segregation of the cleaning process has been due to the inherent chemical and physical incompatibilities between conventional cleaning operations and most assembly tools. Manufacturing operations requiring a cleaning or surface treatment process may include cutting, drilling, trimming, micro-machining, bonding, dicing, abrasive finishing, polishing, stamping and welding, among many other operations. There is a present need for an alternative cleaning model for the manufacturing process. This alternative integrated cleaning into the production process to produce a range of new assembly tools—hybridized cleaning and manufacturing tools. Hybrid tools are much more productive because two or more assembly processes can be performed simultaneously within the same work cell. Substrates being treated don't have to be removed, cleaned and returned to the production line—resulting in reduced human interaction, higher throughput and decreased cost-of-ownership. In the traditional manufacturing model, precision parts cleaning is not considered a value-added operation. The present invention incorporates the cleaning process into the value-added assembly and manufacturing operations, which enhances both product yield and tool productivity. The present invention is suitable for integration into original equipment manufacturer (OEM) tools as well as serving as a stand-alone tool for manufacturing production lines. The present invention enables the creation of unique and useful hybrid manufacturing technology, providing cleaning during manufacturing and assembly operations.